The present invention relates to an outer shroud for use in a gas turbine engine. More particularly, the present invention relates to a means for achieving substantially uniform thermal growth of an outer shroud.
In a gas turbine engine, a static shroud is disposed radially outwardly from a turbine rotor, which includes a plurality of blades radially extending from a disc. The shroud ring at least partially defines a flow path for combustion gases as the gases pass from a combustor through turbine stages. Typically, there is a gap between the shroud ring and rotor blade tips in order to accommodate thermal expansion of the blade during operation of the gas turbine engine. The size of the gap changes during engine operation as the shroud and rotor blades thermally expand in a radial direction in reaction to high operating temperatures. It is generally desirable to minimize the gap between a blade tip and shroud ring in order to minimize the percentage of hot combustion gases that leak through the tip region of the blade. The leakage reduces the amount of energy that is transferred from the gas flow to the turbine blades, which may penalize engine performance. This is especially true for smaller scale gas turbine engines, where tip clearance is a larger percentage of the combustion gas flow path.
Many components in a gas turbine engine, such as a turbine blade and shroud, operate in a non-uniform temperature environment. The non-uniform temperature causes the components to grow unevenly and in some cases, lose their original shape. In the case of a shroud, such uneven deformation may affect the performance of the gas turbine engine because the tip clearance increases as the shroud expands radially outward (away from the turbine blades).